The present invention generally relates luminaires and lighting systems for providing general and specialty lighting, and more particularly to luminaires and lighting systems employing light sources that are relatively bright, such as light emitting diodes (LEDs).
LEDs are increasingly used in lighting applications because of their energy efficiency, that is, their ability to produce a given lumen output per watt consumed. Such light sources are relatively small and intensely bright. For example, an LED that is rated at just ⅛ watt and that produces 30 lumens per watt can have a brightness of between approximately 50,000 to 300,000 candelas per square meter for LED sizes ranging from 25 mm2 down to 4 mm2. For LEDs having higher wattage ratings the brightness increases dramatically.
Often LED are employed in applications where the intense brightness they produce contrasts with surrounding surfaces that are unilluminated or relatively dark. Such brightness contrasts can produce visual discomfort and will, in many applications, be undesirable. The present invention overcomes the problems associated with such contrasts in brightness by providing a unique and versatile optical system and method for managing the brightness of surfaces surrounding relatively bright light sources used by a luminaire or lighting system. The invention manages the brightness contrast between bright light sources and surrounding surfaces that are normally relatively dark without the need to add additional sources of light to illuminate the surrounding surfaces. An optical system in accordance with the invention will also permit a lighting designer to create different distributions of light from the optical system.